• Polymer(Korea)
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• v.24 no.4
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• pp.538-544
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• 2000

The characteristics of cell growth and foamed cell structures of PP were investigated by a continuous foaming process. The operating parameters were the contents of blowing agent and nucleating agent, nucleating agent contents, die temperatures and die dimensions. The foaming cells grew without collapse at less than 14.5 wt% of blowing agent, isopentane. But the cells were collapsed when the blowing agent content was more than 14.5 wt%. The foam density dramatically decreased when a very small amount of the nucleating agent, 1 wt%, was added. After the nucleating agent was added, the cell's weight plummeted to one-seventh of its previous weight. Stable foam cell structures were formed at the die temperature of 17$0^{\circ}C$. However, the effects of the pressure drop rate on the cell morphology were not serious.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.80-85
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• 2016

Carbon fiber-reinforced composite materials have been widely used in various industrial fields, but there are limits to increasing their strength and stiffness, because of the short-length fibers that are impregnated in them. In this study, a lab-scale small extruder system was developed with the capability to perform the carbon fiber impregnation and extrusion process in order to evaluate the properties of long-length carbon fiber reinforced thermoplastic composite materials molded by the LFT-D method. Specimens were made with the small extruder to press-mold long-length carbon fiber composite materials and evaluate their material properties. As a result, it was found that the carbon fiber length, press load and carbon fiber contents have a considerable influence on the strength and stiffness. Additional studies on such factors as the mixing screw design and coating of the carbon fiber are needed in order to improve the mechanical properties of carbon fiber composite materials.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.210-213
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• 1995

In this study,the effect of both process parameters (wheel velocity, friction coefficients between die and billet, etc) and die-shape (abutment height and shape, flash gap, etc.) on the surface defect on forming process is theoretically investigated. For this work, computer simulation was performed by using the DEFORM, a commercial FEM code. Through numerous simulations with different parameters and die shapes, We propose one optimal die shape for CONFORM process which can remove surface defect.

• The Korean Journal of Rheology
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• v.8 no.1
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• pp.11-29
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• 1996

스크류 채널 내에 주기적을 배리어를 설치함으로써 단축 스크류 압출 공정에서의 혼합 성능이 높여질수 있음이 S.J. Kim과 T.H. Kwom에 의해 밝혀진 바있다. 그들은 이새 로운 스크류를 통한 혼합이 카오틱하는 점으로부터 이 새로운 스크류를 카오스 스크류라고 명명했다. 우리는 카오스 스크류가 장착된 단축 압출공정에서 역학계 이론과 혼합운동학을 연계하여 연구를 수행하였다. 포인카레 단면을 통한 연구로부터 우리는 배리어의 배열이 islan의 크기에 대단히 밀접하게 관련되어 있음을 발견하였다. 연속적인 쉘 변형은 카오틱 유동에서 유체 요소를 지수 함수 형태로 늘이는 늘임과 접힘으로 이루어진 카오틱 혼합 메 카니즘을보여준다. 유체요소의 국부 늘임은 원리상으로는 계산되어질수 있으나 수치 해석상 의 어려운 점이 있다. 정규 유동에서와 달리 카오틱 유동에서는 입자 추적이 Runge-Kutta 적분중의 시간간격에 대단히 민감하다. 그래서 실제 사용될수 있는 시간 간격에 의해 계산 된 국부 늘임율 및 혼합효율의 정확도가 보장되어지지 않는다. 이러한 점들을 고려하여 우 리는 새로운 혼합 척도로 $\sigma$z를 제안하는데 이값은 비교적 긴 유체선분이 채널방향을 따라 늘어나는 비에 관련된 값이다. 배리어 영역의 길이가 짧을수록 $\sigma$z는 큰값으로 나타나지만 포인카레 단면에 의한 연구에 따르면 배리어의 주기가 너무 짧다면 두 개의 거대한 island 가 존재하는 것으로 밝혀졌다. 그리고 이러한 사실은 유체요소의 늘임비가 크다는 것이 항 상 좋은 혼합성능을 뜻하는 것은 아니라는 점을 보여준다. 이러한 관점에서 볼 때 혼합 스 크류를 설계하는데 있어서는 포인카레 단면을 병행하여 ${\sigma}_z$의 값을 사용하는 것이 바람직할 것이다.

• Korean Journal of Materials Research
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• v.8 no.7
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• pp.641-647
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• 1998

The machinability properties of P/M 2011 AI alloys extruded rapidly solidified by rotating disc atomization were investigated in this study. The Pb-Bi particles were very uniformly and finely dispersed in the P/M 2011 AI alloys extruded rapidly solidified. According to the increase of cutting speed, the short discontinuous chips were produceed and continuous chips were formed from the lower feed values of O.lmm/rev. The surface roughness is depend on the feed values, not cutting depth and cutting speed. The short discontinuous chips were formed due to dispersed $AI_20_3$ particles and Pb- Bi inclusion.

• The Korean Journal of Rheology
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• v.8 no.3_4
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• pp.177-186
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• 1996

압출가공으로 제조된 Polycarbonate(PC)/Acrylonitrile-Butadiene-Styrene(ABS) 블 렌드의 사출조건에 따른 모폴로지와 기계적 성질의 변화와 그 상관관계를 고찰하였다. 사출 온도와 금형온도가 높아질수록 분산상간의 coalescence 현상이 활발히 진행되었으며 이러한 모폴로지 변화로 인하여블렌드의 인장강도 굴곡강도 그리고 충격강도 등의 기계적 성질이 급격히 저하되었다. 사출온도와 금형온도의 증가에 따른 coalescence의 심화는 높은 온도에 서 연속상과 분산상의 점도가 저하되어 분산상 사이에 존재하는 연속상 성분의 배출이 보다 용이하게 이루어져 나타난 현상으로 설명된다. 실용적으로 특정한 상용화제가 투입되지 않 는 PC/ABS 블렌드를 사출공정을 거쳐 제품을 생산할 경우에는 급격한 모폴로지와 물성변 화가 일어나지 않는 범위에서 사출온도를 유지하는 것이 제품의 품질관리 측면에서 매우 중 요하다.

• Korean Journal of Materials Research
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• v.11 no.7
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• pp.590-598
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• 2001

SiCp/pure Al and SiCp/2024Al MMCs were fabricated by in-situ VHP process designed specially just in this study which is composed of the vacuum hot press at range from R.T. to $500^{\circ}C$ and the continuous extrusion without canning process at $520^{\circ}C$. It was investigated the effect of SiC particle size, volume fraction and extrusion ratio on the tensile properties and micro structure in auf composites. In case of the 10:1 extrusion ratio, but SiCp/pure Al and SiCp/2024Al composites were shown a sound appearance and a good micro structure without crack of SiCp as well as uniform distribution of SiCp. However, in case of the 16:1 extrusion ratio, the number of cracked SiC particles more than increased in a higher volume fraction composite and 2024Al matrix composite compared with pure Al matrix one. The tensile strength of the composites reinforced smaller SiCp was higher than that of the bigger SiCp reinforced in same volume fraction and extrusion ratio.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.7
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• pp.1109-1113
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• 2005

The objective of this study was to determine the effect of extrusion temperature on puffing of white and red ginseng powder. The extrusion variables were feed material (red and white ginseng powder) and die temperature $(100\;and\;115^{\circ}C)$. The analyzed characteristics of ginseng extrudates were sectional expansion index, microstructure and rheological properties. Most of biopolymer was highly puffed at higher extrusion temperature, but the cross-sectional expansion of white and red ginseng powder was higher at 1000e and longitudinal expansion seems to higher at $115^{\circ}C$. White and red ginseng powder were puffed inconsistently and discontinuously at $115^{\circ}C$. The scanning electron microphotograph of extruded white ginseng was uniform air cell distribution at 100oe, but pore size increased at $115^{\circ}C$ and had fine uniformity due to pore explosion. White ginseng and its extrudate were pseudoplastic. Intrinsic viscosity was lower as a result of increased die temperature. The cross-sectional expansion seems to be inconsistent and decreased due to decrease in melt viscosity at $115^{\circ}C$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.104-112
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• 2021

For extrusion processes in the process industry, the need to build smart factories is increasing. However, in most extrusion production sites, the production method is continuous, and because the properties of the data are undeed, it is difficult to process the data. In order to solve this problem, we present a methodology utilizing a near field communication (NFC) sensor rather than water-based data entry. To this end, a wireless network environment was built, and a data management method was designed. A non-contact NFC method was studied for the production performance-data input method, and an analysis method was implemented using the pivot function of the Excel program. As a result, data input using NFC was automated, obtaining a quantitative effect from reducing the operator's data processing time. In addition, using the input data, we present a case where a bottleneck is improved due to quality problems.

• Polymer(Korea)
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• v.26 no.1
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• pp.53-60
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• 2002

Polypropylene(PP : continuous phase)/poly (styrene-co-acrylonitrile)(SAN : dispersed phase) blends, and PP/poly(acrylonitrile-butadiene-styrene) (ABS : dispersed phase)blends, containing various amounts of compatibilizer(PP-SAN graft copolymer), were prepared at various shear rates by using twin-screw extruder. In the PP/SAN blend, the average size of the dispersed particles(SAN) was increased with SAN content, while the flexural strength and tensile strength were decreased with SAN content. When the screw rpm was increased from 10 to 60 rpm, the size of the dispersed phase was decreased while the flexural strength and the tensile strength were increased. Maximum mechanical strength and minimum droplet size were observed when the 5 phr compatibilizer was added to the PP/SAN blends. The mechanical strength of PP/ABS blends such as flexural strength and tensile strength increased by adding compatibilizer was reached maximum when blends contained 5 phr compatibilizer.